Welding helmets are known in the art and generally include a protective shell head covering, a head strap for holding the shell in position on the head, and a lens through which the wearer views the work. One of the more useful and commercially successful improvements to the lens has been the prior development of an auto-darkening lens or shutter assembly. This feature provides a liquid crystal shutter and an electronic circuit for automatically sensing the presence of the welding arc and then darkening the liquid crystal shutter in response thereto so that the welder can keep his helmet in place and continue to have his face protected even while he is not welding, amongst other advantages. Even while in the clear state, the shutter protects the welder's eyes from harmful UV, flying debris, etc, and by providing a shutter that changes its light transmission qualities from dark to light these advantages may be realized.
Over the years, patents have been issued for improvements related to the liquid crystal lens, and the electronic circuitry used to drive the lens or shutter. Examples include U.S. Pat. Nos. 5,074,647; 5,347,383; 5,252,817; 5,248,880; 5,208,688; and others, the disclosures of which are incorporated by reference. This auto-darkening shutter assembly feature has been the focus of much inventive activity at least in part because of the perceived value to the user of keeping the helmet on the user's head and in the operable position to protect the user's eyes and face even if he is not welding. This provides a tremendous safety advantage and can significantly reduce the risk of injury to a skilled welder who would be difficult to replace.
In order to further improve the welding helmet and provide still another feature that will increase the number of work situations and hence the amount of time that a welder can keep his helmet on and in the operable position, and one which will provide the welder with even greater personal control over his helmet and shutter assembly, the inventors herein have succeeded in developing a manual control which permits the welder to fix the shutter shade level and disable the auto-darkening circuit at the same time. The invention allows for two, or more, preselected shutter shade levels to be conveniently chosen by the welder as the helmet remains in place and an indicator light inside the helmet which reminds him which mode he has selected. When these fixed shutter shade levels have been chosen by a manual control, the control does not allow the shutter to convert automatically into the auto-darkening mode. In other words, upon manually selecting a fixed shade setting, the welder has fixed the shade setting until he manually changes the control back into the auto-darkening mode, or for that matter into another fixed shade setting. The shades preferably considered by the inventors to be most useful to a welder are clear (a nominal shade 3 due to the limits of the liquid crystal shutter) and a mid-level shade 5, as said shade levels are known in the art.
The clear shade is chosen to allow the welder to have a relatively clear view through the shutter so that he can get his work ready, and perform any other work related tasks without any substantial impairment of his vision. A shade 5 setting allows a welder to perform certain types of welding which do not generate the extremely bright light of electric resistance welding, such as torch welding as is commonly used in muffler shops, etc. With these kind of welding operations, the welder would ordinarily take his helmet off and switch to goggles or another helmet having a fixed shade 5 lens. This is undesirable as it requires additional equipment, takes time, etc.
The controls preferably used to permit the welder to select these fixed shade settings are a plurality of pushbuttons mounted directly on the same enclosure which houses the shutter, other commonly provided controls and the electronic control circuit contained on one or more circuit boards. Indeed, another aspect to the present invention is the novel arrangement of the pushbutton controls inside the helmet and at the lower end of the control housing so that the welder may conveniently reach up inside the helmet as it remains in an operable and protective position and change the shutter shade setting. The control housing also has a visual indicator which preferably is a two color LED which illuminates amber or green to indicate to the welder that he has manually selected a fixed shade of shutter level illuminates amber or green to indicate to the welder that he has manually selected a fixed shade shutter level. This serves as a constant reminder so that he does not mistakenly take up his welding and expect the shutter to auto-darken. As a further safety feature, the visual indicator preferably goes dark when the auto-darkening mode is selected so that the welder need only be sensitized to whether any light is on to remind him not to expect auto-darkening. In other words, as a reflex the welder need only keep in mind that any visual cue of the illuminated LED means no auto-darkening.
The pushbuttons are preferably provided with one for each fixed shade setting and another for auto-darkening. The control circuit is configured so that each pushbutton only selects that feature, and does not also turn that feature off. In other words, the welder can push the "clear" pushbutton any number of times and all he has done is select the clear shutter shade level. This allows a welder to push any button any number of times and be sure about the shutter shade setting without fear of shutting it off or shifting to any other shade setting. This can be important as welding can be a tough job in an unfriendly environment and the welder's hands likely have thick gloves on them so that as he reaches up into the helmet to make his control setting he should not be asked to make fine distinctions in operating the buttons.
Still another aspect to the present invention is the control housing and arrangement of the circuit boards within the housing and surrounding the shutter assembly. It is important for manufacturing and assembly that the shutter housing be separately made and then assembled to the protective shell. This reduces manufacturing costs and allows the various controls and electronics to be conveniently changed out in the field should the shutter assembly need replacing. This prevents the entire helmet from being discarded should only the electronics fail. However, implementation of the present invention requires additional electronics and it needs to be preferably located in the same housing. The dimensions of the helmet and especially the face and eye portion of the helmet limit the space available for locating these electronics as they are routinely mounted on a printed circuit (PC) board for high speed pre-assembly. However, the now standard controls and circuitry are routinely mounted above the shutter and consume virtually the entirety of that available space. The shutter is generally sized to fill virtually the entirety of the width of the available space near the eye so as to maximize the viewing area for the welder. This creates a problem for adding a PC board below the shutter as the electronics are most conveniently designed for interconnection with the "standard" controls for the auto-darkening feature. In order to solve these and other problems in the prior art, and to allow for the addition of another PC board beneath the shutter that can be interconnected with the existing PC board above the shutter all within a single housing, the inventors have succeeded in designing a housing that is extended in length and has made use of a strap like cable extending between the top PC board and the bottom PC board. The cabling preferably is minimized in size through the minimization of the number of wires needed to interconnect the two boards and is also preferably a flat strap that may be folded over and fit conveniently within the relatively narrow sides of the housing that border the shutter. In this way, the extended lower half of the housing may conveniently house the second PC board and the pushbuttons be mounted directly onto the second PC board, using techniques known in the art. Note that this arrangement also conveniently locates the pushbuttons near the bottom of the housing where they are most accessible for the welder to reach up into the mask and operate.
The electronic circuitry preferably used by the inventors is elegantly simple to minimize cost and the size of the PC board that mounts it. Several features are included in the circuitry which enhance the invention. These include the ability of the preselected shade level settings to be adjusted at the factory so that the manufacturer can conveniently offer a helmet offering a shade 5, or some other shade level as a fixed shade level. By using infinitely variable potentiometers, the shade level setting may be fine tuned to ensure compliance with industry standards regardless of variation in other electrical components. Other circuitry features will be explained in the preferred embodiment.
While the principal advantages and features have been briefly described, a greater understanding of the invention may be attained by referring to the drawings and the detailed description of the preferred embodiment which follows.